Channel Manager

Topic Contents

KOH (Potassium Hydroxide) Preparation

Exam Overview

Doctors use the KOH preparation to find out whether a fungal
infection is present on the nails, skin, scalp, or beard.

A doctor or nurse takes a sample of skin by lightly scraping the
infected area that is scaling or flaking.

The doctor or nurse places the nail, skin, or hair sample on a slide with
potassium hydroxide (KOH) solution and gently heats it. This solution slowly
dissolves the skin cells but not the fungus cells. The fungus cells are then
visible with a microscope. Color stains may be used so that the fungus is
easier to see.

Why It Is Done

A doctor may do a KOH test to find out whether a person
has a fungal infection. Fungal infections may cause:

Ringworm of the scalp or beard. With this infection, a person has flakes of dead skin (dandruff) on the hair; broken, crusted, or
matted hair; redness or irritation of the scalp or beard; swollen areas and
blisterlike bumps with pus (kerions); and/or hair loss.

Ringworm of the skin. With this infection, a person has patches of skin
that are itchy, red, or scaly, with blisterlike bumps on the edges.

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use.
How this information was developed to help you make better health decisions.